The present invention relates to a method for transmitting computer or digitally encoded data over multiple signal transmission means such as a telephone lines in order to increase throughput or decrease the amount of time necessary for the transmission of such data.
Computers manipulate information that has been coded into digital form. The digitally encoded information often needs to be transmitted from a source i.e. where the data is being generated, to a remote location computer, where the data is to be processed, or to a display, where the data is to be viewed.
Digital encoding of information is well known. It means that any information is described in a digital format or as a sequence of ones or zeroes referred to as bits. Most data in nature is first observed in analog form, that is in a gradation of amplitude or other variety of parameters. When such analog data is converted to digital, the number of bits of digital data increases exponentially.
If we were to take a black and white picture of a page of text, such representation is in analog form. To digitize the picture we would divide it into very small squares or rectangles and identify each as a white or black segment or as a one or zero. To get shades of gray and to make the picture appear smooth as opposed to grainy we need to make each of the small squares or rectangles very small. If we are to divide the document into a grid of 320 by 200 lines we come up with 64 thousand individual increments or pixels.
To achieve the illusion of motion or video pictures, the individual still pictures can be altered 30 or more times per second. From the perspective of digitizing we would then need to provide 1.92 mega bits of information per second. If we are to include color instead of black and white, and provide for 256 shades, the number of bits of data required increases further to about 500 mega bits per second, or about 64 mega Bytes.
A video camera or scanner device can generate the data in real time. Devices exist which can digitize the analog data generated by sensor devices such as video cameras. The digitized information is then stored in memory. To transmit the information to another location we need to have some means which can move very large amounts of digital data at the same time, or lacking such means we need to move the data seriatim and take the time until the data is transferred.
At the present time the transmission of video signals has been done typically in analog form, one reason being that it was difficult and slow to transmit such data in digital form.
The existing and convenient method available for the transmission of data is the telephone network. The telephone network consists of a system which combines copper wire with radio, microwave, fiber optic and other transmission means. Due to the limitation of the copper wires and electronic switches inherent in the telephone network, there is presently a limit on the throughput or number of bits per unit time of digital data that can be sent over the telephone lines. That number is between 4800 and 9600 baud (bits per second).
Under current systems if a sensor device is generating digital data at a rate in excess of 9600 baud, the data can not be transmitted over the telephone system in real time. Instead the data must be stored and then transmitted over the telephone system from memory. At the receiving end the data is then fed into another memory where it can be reconstituted for presentation over a display means.
Various means have been suggested to reduce the amount of data being sent and thus reduce the time necessary to transmit such data. These alternative means include methods of data compression, selective data transmission and other shortcuts such that the receiving end, in effect regenerates the information originally observed at the sending end, from the highlights of observed information.
Even with all the data reduction methods, the amount of digital data is such that the constraints or throughput of the current telephone network does not satisfy the need.
This invention teaches a method for overcoming that limitation, and enabling a user to increase the throughput of digitized data over ordinary i.e. existing telephone networks.